1. Field of the Invention
This invention relates generally to the field of electronic device testing and specifically to a relay switching matrix assembly.
2. Description of the Related Art
Electronic instruments are used to test and analyze the performance of electronic equipment, devices, and circuits. A plurality of test leads are connected between selected points in the equipment, device, or circuit and selected instruments to perform the desired tests. To reduce the number of test instruments required and to minimize the need for reconnecting test leads at different points, the leads are connected to the test instruments through a switching matrix. The switching matrix uses a plurality of relays that are controlled to connect selected test leads to selected inputs of the test instruments. During the course of a test the leads may be sequentially connected to several different inputs or instruments by the matrix.
The relays commonly have three switching elements or poles adapted to switch three conductors of the test circuit, typically a pair of signal conductors and a shield. The relays are preferably of the type described in U.S. Pat. No. 5,559,482, assigned to the assignee of this invention and incorporated herein by reference.
The relays are mounted on a printed circuit board with the leads of the relays being soldered to matrix circuits through holes in the board. The matrix circuits include a plurality of input circuits connectable to the device under test through the test leads, and a plurality of pathway circuits connectable to the test instruments by pathway leads. Polytetrafluoroethylene is commonly used as an insulator, creating triboelectric effects. The relays are controlled to interconnect selected input circuits with selected pathway circuits. The switching is done at high speeds to enable a large volume of test data to be collected in a short time. However, the switching must permit time for transient states to settle, allowing testing to be done at a steady state.
Dielectric absorption in the matrix has been a source of errors and delays in reaching a steady state reading during testing. A relay matrix is sought that reduces the dielectric absorption of the prior art matrices. The matrix should be arranged to minimize circuit lengths and insulation required, thereby reducing losses, as well as noise, interference, and other problems. In addition, it is desirable to have an improved switching matrix that provides effective shielding of the circuits and relays to reduce noise and interference. It is also desirable to provide for simple and efficient removal and replacement of relays, which occasionally fail.